In connection with pulse echo-based detection, conventional methods which scan the surroundings of vehicles particularly use acoustical sound waves. One may use the shift in frequency produced by the Doppler effect to detect the speed of objects, specifically the relative speed between a transducer and a reflecting object.
These methods are used particularly for parking systems or generally for driver assistance systems, in each case a transducer covering a sector specific to the transducer. The problem basically exists that a wide sector does cover a wide range of dangers, to be sure, but is not particularly directionally selective, while a narrow sector is directionally selective but covers only a small range of dangers. A plurality of consecutive transducers having small sectors are cost-intensive, however, and are linked to complex mounting.
PCT Application No. WO 07/147,533, a method is described in which modulated transmission pulses, that are emitted using a directional lobe, are used to detect various objects having different Doppler-shifted frequencies. However, the modeling is costly, requires precise and synchronized receiving mechanisms and limits the working distance (because of a minimum modulation frequency that has to be maintained).
Conventional methods for object detection are consequently not directionally selective or they require a large expenditure. It is therefore one object of the present invention to provide a method and a device by which, using simple means, a scanning of the surroundings is provided which permits a high directional resolution or spatial resolution.